EP2602036B1 - Apparatus and method for sintering sinter material - Google Patents

Apparatus and method for sintering sinter material Download PDF

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Publication number
EP2602036B1
EP2602036B1 EP12194369.0A EP12194369A EP2602036B1 EP 2602036 B1 EP2602036 B1 EP 2602036B1 EP 12194369 A EP12194369 A EP 12194369A EP 2602036 B1 EP2602036 B1 EP 2602036B1
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EP
European Patent Office
Prior art keywords
temperature
base plate
tray
sinter
interior chamber
Prior art date
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Application number
EP12194369.0A
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German (de)
French (fr)
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EP2602036A1 (en
Inventor
Jörg Hachenberg
Rudi Steinke
Peter Popp
Irmgard Wissel
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Dentsply Sirona Inc
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Dentsply Sirona Inc
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Publication of EP2602036A1 publication Critical patent/EP2602036A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/003—Apparatus, e.g. furnaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/1003—Use of special medium during sintering, e.g. sintering aid
    • B22F3/1007—Atmosphere
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/1003—Use of special medium during sintering, e.g. sintering aid
    • B22F3/1007—Atmosphere
    • B22F3/101—Changing atmosphere
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F27B14/04—Crucible or pot furnaces adapted for treating the charge in vacuum or special atmosphere
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B17/00—Furnaces of a kind not covered by any preceding group
    • F27B17/02—Furnaces of a kind not covered by any preceding group specially designed for laboratory use
    • F27B17/025—Furnaces of a kind not covered by any preceding group specially designed for laboratory use for dental workpieces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/04—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated adapted for treating the charge in vacuum or special atmosphere
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/10—Muffles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D5/00—Supports, screens, or the like for the charge within the furnace
    • F27D5/0043—Supports specially adapted for dental prosthesis
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D7/00—Forming, maintaining, or circulating atmospheres in heating chambers
    • F27D7/06—Forming or maintaining special atmospheres or vacuum within heating chambers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A61C13/20—Methods or devices for soldering, casting, moulding or melting

Definitions

  • the invention relates to an apparatus for sintering sintered material, according to claim 1 comprising a sintered receiving on a base plate arranged shell with a sintered receiving interior space as the first interior, a cup surrounding the cup-shaped cover whose edge is supported gas-tight relative to the base plate , with the inner space surrounded by the cup-shaped cover as the second inner space Schutzgaszu operations- and -ableitungsö réelle and the cup-shaped cover with base plate surrounding sintered space as the third interior.
  • the invention relates to a method according to claim 8 for sintering of sintered material, such as oxidation susceptible material, in particular metallic sintered material, in particular in the form of a dental framework, using a device comprising a arranged on a base plate shell, in the interior as the first interior of the sintered material is introduced, a cup surrounding the cup-shaped cover, the edge of which is sealed relative to the base plate, as well as with the inner space surrounded by the cover as the second interior Schutzgaszu operations- and -ableitungsö réelle, wherein the surrounded of the cup-shaped cover second interior is purged with inert gas.
  • sintered material such as oxidation susceptible material, in particular metallic sintered material, in particular in the form of a dental framework
  • a device and a method of the type mentioned are the DE 20 2010 007 606 U1 and DE 20 2010 002 533 U1 refer to.
  • a shell made of quartz is raised, are sintered in the dental scaffolds of a silver-palladium alloy or chromium-cobalt alloy.
  • the chimney block and the shell are surrounded by a quartz container, which is sealed by a graphite seal against a base plate, on which the fireclay block is arranged. Both the base plate and the chamotte block are penetrated by holes in order to flush the surrounding of the quartz container interior, within which the quartz shell is located, with inert gas such as argon.
  • the sintering is carried out under a protective gas atmosphere. In this case, occurs at temperatures around 1200 ° C, an undesirable corrosion of the quartz, so that this is previously coated with a boron nitride spray.
  • the material to be sintered is placed in the shell on inert beads of corundum, alumina or zirconia.
  • the corresponding device has the disadvantage that use at temperatures above 1200 ° C is not possible; because on the one hand the life of quartz is very limited at appropriate temperatures and on the other hand, a chipping due to the handling of quartz materials is then determined when an immediate contact with finger fat occurs.
  • the DE 20 2011 106 734 U1 relates to an apparatus for oxygen-free sintering of metal or ceramic and comprises a bottom plate on which a hood is supported. Within the hood, a sintered crucible is supported via a support plate into which sintered material can be introduced. Furthermore, inert gas supply and discharge openings are present. As the material of the apparatus, quartz glass or recrystallized silicon carbide is provided.
  • the WO 94/16642 A1 refers to a kiln in which a combustion chamber is arranged, which is covered on the head side by a lid over which gas can flow when inert gas is introduced into the combustion chamber.
  • Subject of the EP 2 101 133 A1 is a sintering furnace for dental preparations.
  • the DE 10 2008 012 578 A1 refers to a dental oven with which various heating periods are passed through. In this case, an overshoot of the heating power can take place.
  • the DE 20 2011 005 465 U1 refers to an apparatus for oxygen-free sintering of metal or ceramic.
  • sintered material is embedded in a sintered granules present in a sintered container, the z. B. may consist of zirconia beads.
  • the material is introduced into a chamber which is surrounded at a distance by an insulation, which in turn is arranged in the interior of a furnace.
  • the chamber can be fed directly via a line, a gas.
  • a vacuum sintering furnace is out of the JP 2002 372373 A known. Process material is covered by a hood.
  • the present invention has the object, a device and a method of the type mentioned in such a way that the disadvantages of the prior art are avoided, in particular sintering even at temperatures above 1200 ° C can be easily performed. Likewise, it should be ensured that unwanted discoloration or oxidation of the material to be sintered is avoided.
  • the object is essentially achieved in that the shell is covered by a closure element, and that the first interior is closed by a gas flow in the closure element covering the shell with the second interior.
  • the invention relates, inter alia, to an apparatus for sintering sintered material comprising a sintered material receiving on a base plate arranged shell with a sintered material receiving interior space as a first interior, a cup surrounding the cup-shaped cover, the edge of which is sealed against the base plate with the pot-shaped cover surrounded interior as a second interior connected Schutzgaszu operations- and -ableitungsö réelle and the cup-shaped cover with base plate surrounding sintered space as the third interior, which is characterized in that the cup-shaped cover is directly supported gas-tight with its edge on the base plate, that the shell of a closure element is covered, and that the first interior in which the Shell covering closure element is connected gas stream moderately with the second interior.
  • the sintered material is sintered in the interior surrounded by the shell, which is referred to as the first interior space, the shell being covered by a closure element.
  • the first interior space of inert gas can be flowed through, but the risk that disturbances such as oxygen enter the interior of the shell is largely reduced.
  • the cover is supported gas-tight or form-fitting with its edge directly on the base plate.
  • the edge of the cover and the base plate are ground flat to such an extent that the former can rest directly on the base plate without additional gasket to seal to an extent that allows oxygen to penetrate into and out of the cover designated interior basically not or not substantially possible.
  • At least the shell and its closing element such as cover, but in particular base plate, shell, closure element and cup-shaped or dome-shaped or bell-shaped cover consists of a material from the group SiC, SiN.
  • This selection of materials offers the advantage that sintering can be carried out at temperatures above 1200 ° C., in particular up to 1350 ° C., without damaging the materials.
  • SiC is particularly preferably used because it has a reducing effect on oxygen.
  • penetration of oxygen into the (second) interior of the cover is difficult.
  • a development of the invention provides that the shell is supported on a perforations having ring, which in turn is arranged on the base plate, wherein preferably the base plate is penetrated within the ring of the protective gas supply opening and optionally the protective gas discharge opening.
  • projections preferably at least three projections arranged uniformly on a circle, emerge from the shell or its bottom wall, via which the shell is supported on the base plate.
  • the base plate can have a constant thickness over the entire surface, so that the risk of cracking due to the temperature changes occurring during sintering is omitted.
  • the invention is characterized in that the sintered material is stored in the shell on bulk material, which consists of solid balls of ceramic, in particular zirconium oxide or aluminum oxide.
  • ceramic in particular zirconium oxide or aluminum oxide.
  • this initial release of oxygen has no negative effect and can serve as a reducing and indicator in the following, since this effect is reversible in the case of an oxygen breakdown.
  • the sintered material is arranged in a shell with this occlusive closure element, it being ensured that the (first) interior of the shell receiving the sintered material is flushed with a protective gas for the removal of any oxygen present.
  • the closure element acts like a lid or is such.
  • closure element covering the shell is not arranged tightly on the shell, it would also be possible for it to be tightly seated, provided, for example, B. in the closure element itself z. B. formed by laser fine holes are provided through which a protective gas exchange is possible.
  • the materials are suitable for sintering at high temperatures, wherein, in particular due to the reducing effect, silicon carbide must be emphasized.
  • silicon nitride may optionally be used as well.
  • a method of the type mentioned above is characterized in that the shell is covered after introduction of the sintered material in this by a closure element, so that over or at least via an opening in the closure element or via an opening in the shell shielding gas into the interior of the shell, so the first interior, Penetrates that the cup-shaped cover is directly supported gas-tight with its edge on the base plate, and that the surrounded by the cup-shaped cover second interior is acted upon by a lifting of the cover excluding overpressure with the protective gas, in particular with an overpressure p with 1 mbar ⁇ p ⁇ 25 mbar, in particular 2 mbar ⁇ p ⁇ 10 mbar above ambient pressure.
  • a larger object in particular a dental bridge framework, in particular a bridge framework with at least three bridge members, preferably at least five bridge members, is used, and that the sintered material in a device receiving, so these surrounding sintering chamber of room temperature T Z to a temperature T 1 at 800 ° C ⁇ T 1 ⁇ 1100 ° C with a heating rate R 1 with 5 K / min ⁇ R 1 ⁇ 100 K / min, in particular 20 K / min ⁇ R 1 ⁇ 80 K / min, heated , after optionally a holding time t 1 at the temperature T 1 with 1 min ⁇ t 1 ⁇ 10 min to a temperature T 2 at 1200 ° C ⁇ T 2 ⁇ 1350 ° C with a heating rate R 2 with 5 / min ⁇ R 2 ⁇ 30 K / min is heated, the sintered material at the temperature T 2 for a time t 2 with 5 min ⁇ t 2 ⁇ 120 min, in particular 15 min ⁇ t2 ⁇ 50
  • the invention also provides that the sintered material for sintering in a sintering space surrounding the device from room temperature to a temperature T 2 such as 1200 ° C ⁇ T 2 ⁇ 1350 ° C is heated at a heating rate R 1 , at the temperature T 2 via a Time t 2 with 5 min ⁇ t 2 ⁇ 220 min, in particular 15 min ⁇ t 2 ⁇ 60 min is maintained, where appropriate, the sintered material then, ie after the holding time, to a temperature T 3 with T 3 > T 2 for superficial melting is then heated from the temperature T 2 or T 3 to a temperature below 400 ° C at a cooling rate R 3 , wherein the cooling rate R 3 is preferably initially 5 K / min ⁇ R 3 ⁇ 100 K / min is.
  • the heating rate R 1 is set to a value of 5 K / min ⁇ R 1 ⁇ 100 K / min, in particular 20 K / min ⁇ R 1 ⁇ 80 K / min.
  • the heating to a temperature T 1 and the optionally held at the temperature T 1 , and then further heated to a temperature T 2 is preferably carried out for larger objects such as bridge frameworks.
  • the initial heating to the temperature T 1 and then to the temperature T 2 with a possibly different heating rate can be changed to the effect that directly to a temperature T 2 takes place, if it is the sintered to smaller objects, such as a scaffold for a tooth, act.
  • the sintering space may be the interior of a sintering furnace, which may be referred to as a third interior space.
  • the Schutzgaseinlass- and / or -auslassö réelle is connected to an inlet and outlet, which consists of aluminum oxide.
  • the line can be connected to the base plate with a high-temperature adhesive, in particular based on alumina.
  • SiC As the material for the base plate, the cover, the shell and its closure element, one makes use of the good thermal conductivity and almost complete tightness of the material. As a result, temperature differences within the components are minimized. Thermal stresses are thereby reduced. As a result, rapid temperature changes even with large components of z. B. diameter of 100 mm possible. Further, SiC exhibits a reducing effect and is capable of converting residual oxygen in the atmosphere with the contained carbon to carbon monoxide. This effect is not lost. At the same time, no measurable decrease in the wall thicknesses of the materials can be detected.
  • the storage of the sintered material in a not sealed sealed sintering bowl improves the sintering result.
  • the reason for the improvement may be the creation of an interior provided with reducing-wall oxygen. There is a weakening of the disturbance by oxygen. Corresponding disturbances can no longer reach the sintered material directly. It increases the probability that the disturbances are washed out and thus mitigated.
  • the controlled supply and removal of inert gas ensures that the internal pressure in the cover can not rise so that it is raised. In this way, an oxygen exclusion succeeds.
  • one or more protective gas discharge openings in the base plate can also in the cover z.
  • no hollow balls are used for storing the sintered material in the shell.
  • Hollow balls can store oxygen and thus poison the atmosphere in the immediate vicinity of the sintered material at high temperatures.
  • dense spheres are used which can not store oxygen.
  • zirconium oxide is surprisingly suitable as the material for the spheres, although this initially tends to give off oxygen in an oxygen-poor atmosphere. After the oxygen release, the z. B. achieved by a temperature cycle, corresponding solid spheres of zirconia show reducing effect for oxygen.
  • the prior art usually provides for steps. From this, the invention dissolves and uses a flat plate which can be easily polished in the area of the contact surfaces with the cover so that a seal is made to an extent that the penetration of oxygen is basically not or not substantially possible. Since there are no steps, there are no differences in thickness in the base plate, as a result, thermal stresses are reduced.
  • a device 10, 100 is shown purely in principle, are sintered with the metallic sintered material, in particular toothed scaffolds.
  • the device 10 is - corresponding to the device 100 - in an inner or sintered space 12 of a sintering furnace, of which sections of walls 15, 17 are shown in principle.
  • the required temperatures are set to sinter in the apparatus 10, 100 existing sintered material to the extent required.
  • the device 10 consists of a base plate 14, a bell to be designated cup or dome-shaped cover 16, a sectionally U-shaped shell 18 and a lid 20 designated as a closure element, by means of which the shell 18 is not completely sealed in principle.
  • the shell 18 is supported on the base plate 14 via a ring element 22.
  • the ring element 22 has recesses 24, 26, 28, so that a connection between the space surrounded by the bell 16 interior 30 - referred to as the second interior - and the area surrounded by the ring member 22 space 32 consists.
  • the in Fig. 1 arranged sintered material, not shown.
  • the base plate 14, the bell 16, the shell 18, the cover 20 and the ring member 22 are preferably made of SiC, same as SiN may come as alternative materials.
  • the base plate 14 and the peripheral edge 36 of the bell 16 are ground flat in a circumference that a positive standing up of the bell 16 is secured to the base plate 14. As a result, an intrusion of oxygen is basically prevented.
  • the cover 20 should not completely seal off the (first) inner space 34 of the shell 18, so that fluidically a connection between the (second) inner space 30, which extends between the shell 18 and the bell 16, with that of the shell 18 surrounding first interior 34 consists. If the cover 20 sealingly rests on the shell 18, then the cover 20 has at least one opening, so that a flushing of the interior 34 of the shell 18 can take place. Equivalent would be an opening in the shell 18th
  • the second internal space 30 is provided with an inert gas, such as an opening 38, provided in the base plate 14 in the exemplary embodiment. Supplied with argon or nitrogen.
  • This protective gas enters the first inner space 34 surrounded by the shell 18, since, as mentioned, the cover 20 does not seal the shell 18.
  • the protective gas passes through the at least one opening in the cover 20 and / or in the wall of the shell 18th
  • the gas supplied to the second internal space 30 then flows out via an opening which is likewise preferably present in the base plate 14.
  • an opening which is likewise preferably present in the base plate 14.
  • the outflowing gas is preferably directed into the sintering space 12 - that is, the third interior space - in such a way that the bell 16 is surrounded with inert gas at least in the region of its peripheral edge 30.
  • the (second) inner space 30 should have an increased pressure relative to the environment, with an overpressure between 1 mbar and 25 mbar, in particular between 2 mbar and 10 mbar, being preferred.
  • Fig. 2 is different from that of Fig. 1 to the effect that the shell 18 is not supported on a ring 22, but on protrusions 42, 44 protruding from the bottom wall 40 of the shell 18.
  • three projections are provided, which are arranged distributed uniformly on a circle. Otherwise, the embodiment corresponds to the Fig. 1 , so that reference is made to the relevant explanations.
  • the base plate 14 has a constant thickness, so that differences in thickness avoided and as a result internal stresses are reduced.
  • a spherical bulk material 50 is introduced on the inner side 48 of the bottom wall 40, ie the bottom surface, which consists of solid spheres, ie not of hollow spheres.
  • materials are preferably alumina or zirconia in question.
  • the solid balls have the advantage that oxygen can not be stored. This also applies to zirconium oxide spheres, which initially tend to release oxygen in an oxygen-poor atmosphere. After the release of oxygen, however, these show a reducing effect.
  • Base plate 14 Diameter 90 mm to 110 mm, thickness 2 to 4 mm
  • Bell 16 Outer diameter 95 mm to 105 mm, wall thickness 3 mm to 5 mm, height 50 mm to 55 mm
  • Ring element 22 4 mm to 8 mm, outer diameter 60 mm to 70 mm, wall thickness 3 mm to 5 mm
  • Sinter tray 18 Height 30 mm to 35 mm, outside diameter 80 mm to 90 mm, wall thickness 3 mm to 5 mm
  • Cover 20 equal outer diameter shell 18, thickness in the edge region 2 mm to 5 mm, thickness center region 4 mm to 8 mm.
  • the distance between the outer surface of the shell 18 and the inner surface of the bell 16 can be chosen to be relatively small. This has the advantage that in this way the penetration of oxygen into the (first) interior 34 of the shell 18 is additionally hindered, in particular when the protective gas outlet opening is located in the edge region of the bell 16 and passes through it.
  • Fig. 3 Of the Fig. 3 is to take a heating and cooling curve to sinter the sintered 46.
  • the curve according to Fig. 3 applies to a larger object that is to be sintered.
  • An example is a dental bridge framework with 4 members.
  • the sintered 46 is first heated from room temperature T Z to a temperature T 1 , wherein T 1 between 800 ° C and 1100 ° C for cobalt-chromium alloys as material for the sintered 46 lies.
  • the heating rate should preferably be between 20 K / min and 80 K / min.
  • the sintered material 46 is held for a time t 1 between 1 min and 10 min.
  • the sintered material 46 is kept for a time t 2 between 5 and 120 minutes and then cooled to a temperature below 400 ° C, wherein at least a cooling rate between 5 K / min and 100 K / min is to be selected.
  • the device 10, 100 is removed from the sintering space 12.
  • the device 10, 100 can be lowered, as symbolized by the double arrow 52.
  • the sintered body can be produced by cooling to the temperature T 1 for a time between 1 min and 10 min at the temperature T 1 is kept. Then it is cooled to room temperature T Z.
  • the sintered material after reaching the sintering temperature T 2 short-term to a higher temperature T 3 (dashed area) are heated to achieve a superficial melting.
  • the brief targeted melting can be carried out during the holding time t 2 , preferably after the holding time t 2 . The latter results from the Fig. 3 ,
  • the heating to the temperature T 1 holding at this temperature and then the further heating to the temperature T 2 with possibly different heating rates when sintering small objects, such as a framework for a tooth, is not required. Rather, a direct heating from the room temperature to the temperature T 2 take place. Irrespective of this, it is likewise possible to carry out a short-term temperature increase to a temperature T 3 after holding at the temperature T 2 in order to achieve superficial melting of the sintered material.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Oral & Maxillofacial Surgery (AREA)
  • Clinical Laboratory Science (AREA)
  • Powder Metallurgy (AREA)
  • Dental Prosthetics (AREA)
  • Dental Tools And Instruments Or Auxiliary Dental Instruments (AREA)

Description

Die Erfindung bezieht sich auf eine Vorrichtung zum Sintern von Sintergut, gemäß Anspruch 1 umfassend eine das Sintergut aufnehmende auf einer Basisplatte angeordnete Schale mit einem das Sintergut aufnehmenden Innenraum als ersten Innenraum, eine die Schale umgebende topfförmige Abdeckung, deren Rand gegenüber der Basisplatte gasdicht abgestützt ist, mit von der topfförmigen Abdeckung umgebenem Innenraum als zweiten Innenraum verbundene Schutzgaszuführungs- und -ableitungsöffnung sowie die topfförmige Abdeckung mit Basisplatte umgebenden Sinterraum als dritten Innenraum.The invention relates to an apparatus for sintering sintered material, according to claim 1 comprising a sintered receiving on a base plate arranged shell with a sintered receiving interior space as the first interior, a cup surrounding the cup-shaped cover whose edge is supported gas-tight relative to the base plate , with the inner space surrounded by the cup-shaped cover as the second inner space Schutzgaszuführungs- and -ableitungsöffnung and the cup-shaped cover with base plate surrounding sintered space as the third interior.

Ferner nimmt die Erfindung Bezug auf ein Verfahren gemäß Anspruch 8 zum Sintern von Sintergut, wie oxidationsanfälligem Material, insbesondere metallischem Sintergut, insbesondere in Form eines Zahngerüstes, unter Verwendung einer Vorrichtung umfassend eine auf einer Basisplatte angeordnete Schale, in deren Innenraum als ersten Innenraum das Sintergut eingebracht wird, eine die Schale umgebende topfförmige Abdeckung, deren Rand gegenüber der Basisplatte abgedichtet ist, sowie mit von der Abdeckung umgebenem Innenraum als zweiten Innenraum verbundene Schutzgaszuführungs- und -ableitungsöffnung, wobei der von der topfförmigen Abdeckung umgebene zweite Innenraum mit Schutzgas durchspült wird.Furthermore, the invention relates to a method according to claim 8 for sintering of sintered material, such as oxidation susceptible material, in particular metallic sintered material, in particular in the form of a dental framework, using a device comprising a arranged on a base plate shell, in the interior as the first interior of the sintered material is introduced, a cup surrounding the cup-shaped cover, the edge of which is sealed relative to the base plate, as well as with the inner space surrounded by the cover as the second interior Schutzgaszuführungs- and -ableitungsöffnung, wherein the surrounded of the cup-shaped cover second interior is purged with inert gas.

Eine Vorrichtung und ein Verfahren der eingangs genannten Art sind der DE 20 2010 007 606 U1 und DE 20 2010 002 533 U1 zu entnehmen. Hierzu wird in einem Sinterofen auf einem Schamottblock eine aus Quarz bestehende Schale aufgeständert, in der Dentalgerüste aus einer Silber-Palladium-Legierung oder Chrom-Kobalt-Legierung gesintert werden. Der Schamottblock und die Schale werden von einem Quarzbehälter umgeben, der über eine Graphitdichtung gegenüber einer Basisplatte abgedichtet ist, auf der der Schamottblock angeordnet ist. Sowohl die Basisplatte als auch der Schamottblock werden von Bohrungen durchsetzt, um den von dem Quarzbehälter umgebenen Innenraum, innerhalb dessen sich die Quarzschale befindet, mit Schutzgas wie Argon zu durchspülen. Um eine Oxidation der Gerüste zu vermeiden, wird das Sintern unter Schutzgasatmosphäre durchgeführt. Dabei tritt bei Temperaturen um 1200 °C eine unerwünschte Korrosion des Quarzes auf, so dass dieses zuvor mit einem Bornitridspray beschichtet wird. Das zu sinternde Material wird in der Schale auf inerten Kügelchen aus Korund, Alumina oder Zirkonia gelegt.A device and a method of the type mentioned are the DE 20 2010 007 606 U1 and DE 20 2010 002 533 U1 refer to. For this purpose, in a sintering furnace on a Schamottblock a shell made of quartz is raised, are sintered in the dental scaffolds of a silver-palladium alloy or chromium-cobalt alloy. The chimney block and the shell are surrounded by a quartz container, which is sealed by a graphite seal against a base plate, on which the fireclay block is arranged. Both the base plate and the chamotte block are penetrated by holes in order to flush the surrounding of the quartz container interior, within which the quartz shell is located, with inert gas such as argon. In order to avoid oxidation of the frameworks, the sintering is carried out under a protective gas atmosphere. In this case, occurs at temperatures around 1200 ° C, an undesirable corrosion of the quartz, so that this is previously coated with a boron nitride spray. The material to be sintered is placed in the shell on inert beads of corundum, alumina or zirconia.

Die entsprechende Vorrichtung zeigt den Nachteil, dass ein Einsatz bei Temperaturen oberhalb 1200 °C nicht möglich ist; denn zum einen ist die Lebensdauer von Quarz bei entsprechenden Temperaturen stark begrenzt und zum anderen ist ein Abplatzen auf Grund des Hantierens der Quarzmaterialien dann festzustellen, wenn eine unmittelbare Berührung mit Fingerfett erfolgt.The corresponding device has the disadvantage that use at temperatures above 1200 ° C is not possible; because on the one hand the life of quartz is very limited at appropriate temperatures and on the other hand, a chipping due to the handling of quartz materials is then determined when an immediate contact with finger fat occurs.

Die DE 20 2011 106 734 U1 bezieht sich auf eine Vorrichtung zum sauerstofffreien Sintern von Metall oder Keramik und umfasst eine Bodenplatte, auf der eine Haube abgestützt ist. Innerhalb der Haube ist über eine Trägerplatte ein Sintertiegel abgestützt, in den Sintergut einbringbar ist. Ferner sind Schutzgaszuführungs- und - ableitungsöffnungen vorhanden. Als Material der Vorrichtung ist Quarzglas oder rekristallisiertes Siliziumkarbid vorgesehen.The DE 20 2011 106 734 U1 relates to an apparatus for oxygen-free sintering of metal or ceramic and comprises a bottom plate on which a hood is supported. Within the hood, a sintered crucible is supported via a support plate into which sintered material can be introduced. Furthermore, inert gas supply and discharge openings are present. As the material of the apparatus, quartz glass or recrystallized silicon carbide is provided.

Die WO 94/16642 A1 bezieht sich auf einen Brennofen, in dem eine Brennkammer angeordnet ist, die kopfseitig von einem Deckel abgedeckt ist, über den Gas dann strömen kann, wenn in die Brennkammer Schutzgas eingeleitet wird.The WO 94/16642 A1 refers to a kiln in which a combustion chamber is arranged, which is covered on the head side by a lid over which gas can flow when inert gas is introduced into the combustion chamber.

Gegenstand der EP 2 101 133 A1 ist ein Sinterofen für Dentalpräparate.Subject of the EP 2 101 133 A1 is a sintering furnace for dental preparations.

Die DE 10 2008 012 578 A1 bezieht sich auf einen Dentalofen, mit dem verschiedene Aufheizperioden durchfahren werden. Dabei kann ein Überschwingen der Heizleistung erfolgen.The DE 10 2008 012 578 A1 refers to a dental oven with which various heating periods are passed through. In this case, an overshoot of the heating power can take place.

Die DE 20 2011 005 465 U1 bezieht sich auf eine Vorrichtung zum sauerstofffreien Sintern von Metall oder Keramik. Dabei wird Sintergut in einem in einem Sinterbehälter vorhandenen Sintergranulat eingebettet, das z. B. aus Zirkonkügelchen bestehen kann.The DE 20 2011 005 465 U1 refers to an apparatus for oxygen-free sintering of metal or ceramic. In this case, sintered material is embedded in a sintered granules present in a sintered container, the z. B. may consist of zirconia beads.

Der EP-A 0 524 438 A2 sind ein Verfahren und eine Vorrichtung zum Sintern extrudierten Materials zu entnehmen. Dabei wird das Material in eine Kammer eingebracht, die beabstandet von einer Isolierung umgeben ist, die ihrerseits im Innenraum eines Ofens angeordnet ist. Dabei kann der Kammer unmittelbar über eine Leitung ein Gas zugeführt werden. Alternativ besteht die Möglichkeit, dass in die Kammer über deren Abstützung auf einer Basisplatte Gas einströmt.Of the EP-A 0 524 438 A2 A method and apparatus for sintering extruded material is disclosed. In this case, the material is introduced into a chamber which is surrounded at a distance by an insulation, which in turn is arranged in the interior of a furnace. In this case, the chamber can be fed directly via a line, a gas. Alternatively, there is the possibility that flows into the chamber via the support on a base plate gas.

Ein Vakuumsinterofen ist aus der JP 2002 372373 A bekannt. Zu prozessierendes Material ist von einer Haube abgedeckt.A vacuum sintering furnace is out of the JP 2002 372373 A known. Process material is covered by a hood.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, eine Vorrichtung und ein Verfahren der eingangs genannten Art so weiterzubilden, dass die Nachteile des Standes der Technik vermieden werden, insbesondere ein Sintern auch bei Temperaturen oberhalb von 1200 °C problemlos durchgeführt werden kann. Gleichfalls soll sichergestellt werden, dass unerwünschte Verfärbungen oder eine Oxidation des Sinterguts unterbleibt.The present invention has the object, a device and a method of the type mentioned in such a way that the disadvantages of the prior art are avoided, in particular sintering even at temperatures above 1200 ° C can be easily performed. Likewise, it should be ensured that unwanted discoloration or oxidation of the material to be sintered is avoided.

Vorrichtungsgemäß wird die Aufgabe im Wesentlichen dadurch gelöst, dass die Schale von einem Verschlusselement abgedeckt ist, und dass der erste Innenraum bei die Schale abdeckendem Verschlusselement mit dem zweiten Innenraum gasstrommäßig verbunden ist.According to the device, the object is essentially achieved in that the shell is covered by a closure element, and that the first interior is closed by a gas flow in the closure element covering the shell with the second interior.

Die Erfindung bezieht sich u.a. auf eine Vorrichtung zum Sintern von Sintergut, umfassend eine das Sintergut aufnehmende auf einer Basisplatte angeordnete Schale mit einem das Sintergut aufnehmenden Innenraum als ersten Innenraum, eine die Schale umgebende topfförmige Abdeckung, deren Rand gegenüber der Basisplatte abgedichtet ist, mit von der topfförmigen Abdeckung umgebenem Innenraum als zweiten Innenraum verbundene Schutzgaszuführungs- und -ableitungsöffnung sowie die topfförmige Abdeckung mit Basisplatte umgebenden Sinterraum als dritten Innenraum, die sich dadurch auszeichnet, dass die topfförmige Abdeckung unmittelbar mit ihrem Rand gasdicht auf der Basisplatte abgestützt ist, dass die Schale von einem Verschlusselement abgedeckt ist, und dass der erste Innenraum bei dem die Schale abdeckenden Verschlusselement mit dem zweiten Innenraum gasstrommäßig verbunden ist.The invention relates, inter alia, to an apparatus for sintering sintered material comprising a sintered material receiving on a base plate arranged shell with a sintered material receiving interior space as a first interior, a cup surrounding the cup-shaped cover, the edge of which is sealed against the base plate with the pot-shaped cover surrounded interior as a second interior connected Schutzgaszuführungs- and -ableitungsöffnung and the cup-shaped cover with base plate surrounding sintered space as the third interior, which is characterized in that the cup-shaped cover is directly supported gas-tight with its edge on the base plate, that the shell of a closure element is covered, and that the first interior in which the Shell covering closure element is connected gas stream moderately with the second interior.

Auf Grund der erfindungsgemäßen Lehre erfolgt ein Sintern des Sinterguts in dem von der Schale umgebenen Innenraum, der als erster Innenraum bezeichnet wird, wobei die Schale von einem Verschlusselement abgedeckt ist. Ungeachtet dessen ist der erste Innenraum von Inertgas durchströmbar, jedoch wird das Risiko, dass Störungen wie Sauerstoff in das Innere der Schale gelangen, weitgehend reduziert.On the basis of the teaching according to the invention, the sintered material is sintered in the interior surrounded by the shell, which is referred to as the first interior space, the shell being covered by a closure element. Despite this, the first interior space of inert gas can be flowed through, but the risk that disturbances such as oxygen enter the interior of the shell is largely reduced.

Insbesondere ist vorgesehen, dass die Abdeckung unmittelbar mit ihrem Rand gasdicht bzw. formschlüssig auf der Basisplatte abgestützt ist. Der Rand der Abdeckung sowie die Basisplatte werden in einem Umfang plan geschliffen, dass erstere ohne zusätzliche Dichtung unmittelbar auf der Basisplatte aufliegen kann, um in einem Umfang eine Abdichtung zu erzielen, dass ein Eindringen von Sauerstoff in den von der Abdeckung umschlossenen und als zweiter Innenraum bezeichneten Innenraum dem Grunde nach nicht oder nicht wesentlich möglich ist.In particular, it is provided that the cover is supported gas-tight or form-fitting with its edge directly on the base plate. The edge of the cover and the base plate are ground flat to such an extent that the former can rest directly on the base plate without additional gasket to seal to an extent that allows oxygen to penetrate into and out of the cover designated interior basically not or not substantially possible.

Durch diese Maßnahmen ist sichergestellt, dass Sauerstoff von außen in den (zweiten) Innenraum der Abdeckung, die auch als Glocke bezeichnet werden kann, und folglich auch in den von der Schale umgebenden (ersten) Innenraum nicht oder weitgehend nicht gelangt.By these measures it is ensured that oxygen from the outside in the (second) interior of the cover, which can also be referred to as a bell, and consequently in the surrounding of the shell (first) interior does not or not largely.

Hervorzuheben ist des Weiteren, dass zumindest die Schale und deren Verschlusselement wie Deckel, insbesondere jedoch Basisplatte, Schale, Verschlusselement und topfförmige oder haubenförmige oder glockenförmige Abdeckung aus einem Material aus der Gruppe SiC, SiN besteht. Durch diese Materialauswahl ergibt sich der Vorteil, dass ein Sintern bei Temperaturen oberhalb von 1200 °C, insbesondere bis 1350 °C durchgeführt werden kann, ohne dass die Materialien Schaden nehmen. Besonders bevorzugt wird SiC verwendet, da es gegenüber Sauerstoff einen reduzierenden Effekt zeigt.It should also be emphasized that at least the shell and its closing element such as cover, but in particular base plate, shell, closure element and cup-shaped or dome-shaped or bell-shaped cover consists of a material from the group SiC, SiN. This selection of materials offers the advantage that sintering can be carried out at temperatures above 1200 ° C., in particular up to 1350 ° C., without damaging the materials. SiC is particularly preferably used because it has a reducing effect on oxygen.

Das in den Zwischenraum zwischen Schale und topfförmiger Abdeckung eingeleitete Inertgas, bei dem es sich insbesondere um Argon, gegebenenfalls aber auch um Stickstoff handeln sollte, kann nach einer Weiterbildung der Erfindung aus dem zweiten Innenraum, der von der Abdeckung umgeben ist, unmittelbar in den die Basisplatte und die Abdeckung umgebenden Sinterraum, also als dritter Innenraum bezeichneten Innenraum eines Sinterofens geführt werden. Dies resultiert in einer weiteren Konzentrationsabsenkung des Sauerstoffs im Sinterraum (dritter Innenraum) des Sinterofens. Auch ein Eindringen von Sauerstoff in den (zweiten) Innenraum der Abdeckung wird erschwert.The introduced into the space between the shell and cup-shaped cover inert gas, which should be in particular argon, but possibly also be nitrogen, according to a development of the invention from the second interior, which is surrounded by the cover, directly into the Base plate and the cover surrounding sintered space, so be referred to as the third interior interior of a sintering furnace. This results in a further reduction in the concentration of oxygen in the sintering space (third interior) of the sintering furnace. Also, penetration of oxygen into the (second) interior of the cover is difficult.

Eine Weiterbildung der Erfindung sieht vor, dass die Schale auf einem Durchbrüche aufweisenden Ring abgestützt ist, der seinerseits auf der Basisplatte angeordnet ist, wobei vorzugsweise die Basisplatte innerhalb des Rings von der Schutzgaszuführungsöffnung und gegebenenfalls der Schutzgasableitungsöffnung durchsetzt ist.A development of the invention provides that the shell is supported on a perforations having ring, which in turn is arranged on the base plate, wherein preferably the base plate is penetrated within the ring of the protective gas supply opening and optionally the protective gas discharge opening.

Alternativ wird vorgeschlagen, dass von der Schale bzw. deren Bodenwandung Vorsprünge, vorzugsweise zumindest drei gleichmäßig auf einem Kreis angeordnete Vorsprünge, ausgehen, über die die Schale auf der Basisplatte abgestützt ist.Alternatively, it is proposed that projections, preferably at least three projections arranged uniformly on a circle, emerge from the shell or its bottom wall, via which the shell is supported on the base plate.

Durch die diesbezüglichen Maßnahmen ist sichergestellt, dass die Basisplatte eine über die gesamte Fläche gleichbleibende Dicke aufweisen kann, so dass die Gefahr von Rissbildungen auf Grund der beim Sintern auftretenden Temperaturänderungen unterbleibt.By the relevant measures it is ensured that the base plate can have a constant thickness over the entire surface, so that the risk of cracking due to the temperature changes occurring during sintering is omitted.

Des Weiteren zeichnet sich die Erfindung dadurch aus, dass das Sintergut in der Schale auf Schüttgut gelagert wird, das aus Vollkugeln aus Keramik, insbesondere Zirkoniumoxid oder Aluminiumoxid besteht. Bei Zirkoniumdioxid ergibt sich der Vorteil, dass sich dieses unter Sauerstoffabschluss teilweise zu Zirkoniummonooxid umwandelt. Die durch den Sauerstoffmangel entstehenden Fehlstellen führen zu einer dunklen Verfärbung.Furthermore, the invention is characterized in that the sintered material is stored in the shell on bulk material, which consists of solid balls of ceramic, in particular zirconium oxide or aluminum oxide. With zirconium dioxide, there is the advantage that this partly converts to zirconium monooxide with the exclusion of oxygen. The resulting from the lack of oxygen defects lead to a dark discoloration.

Überraschenderweise hat diese anfängliche Sauerstoffabgabe keinen negativen Effekt und kann im Folgenden reduzierend und als Indikator dienen, da dieser Effekt im Falle eines Sauerstoffeinbruchs reversibel ist.Surprisingly, this initial release of oxygen has no negative effect and can serve as a reducing and indicator in the following, since this effect is reversible in the case of an oxygen breakdown.

Aufgrund der erfindungsgemäßen Lehre wird sichergestellt, dass ein Sintern von Metalllegierungen, insbesondere Kobalt-Chrom-Legierungen wie Kobalt-Chrom-Molybdän-Legierungen, bei Temperaturen von 1200 °C und mehr, insbesondere um 1250 °C, durchgeführt werden kann, ohne dass die Gefahr von Oxidation und unkontrollierten Verfärbungen besteht. Dabei wird das Sintergut in einer Schale mit diese verschließendem Verschlusselement angeordnet, wobei sichergestellt ist, dass der das Sintergut aufnehmende (erste) Innenraum der Schale mit einem Schutzgas zum Wegführen von gegebenenfalls vorhandenem Sauerstoff durchspült wird. Das Verschlusselement wirkt wie ein Deckel bzw. ist ein solcher.Due to the teaching of the invention it is ensured that sintering of metal alloys, in particular cobalt-chromium alloys such as cobalt-chromium-molybdenum alloys, at temperatures of 1200 ° C and more, in particular around 1250 ° C, can be performed without the Danger of oxidation and uncontrolled discoloration exists. In this case, the sintered material is arranged in a shell with this occlusive closure element, it being ensured that the (first) interior of the shell receiving the sintered material is flushed with a protective gas for the removal of any oxygen present. The closure element acts like a lid or is such.

Ist bevorzugterweise das die Schale abdeckende Verschlusselement nicht dicht auf der Schale angeordnet, so könnte auch ein dichtes Aufliegen erfolgen, sofern z. B. in dem Verschlusselement selbst z. B. durch Laser ausgebildete feine Bohrungen vorgesehen sind, durch die ein Schutzgasaustausch möglich ist.If the closure element covering the shell is not arranged tightly on the shell, it would also be possible for it to be tightly seated, provided, for example, B. in the closure element itself z. B. formed by laser fine holes are provided through which a protective gas exchange is possible.

Zusätzlich besteht die Möglichkeit, die topf- oder glockenförmige Abdeckung, also die sogenannte Glocke von Schutzgas zu umspülen, das aus dem (zweiten) Innenraum der Abdeckung nach außen geführt wird.In addition, it is possible to surround the pot-shaped or bell-shaped cover, that is to say the so-called bell of protective gas, which is led out of the (second) interior of the cover to the outside.

Insbesondere ist auch von Vorteil, dass die Materialien für ein Sintern bei hohen Temperaturen geeignet sind, wobei insbesondere auf Grund der reduzierenden Wirkung Siliziumcarbid hervorzuheben ist. Alternativ ist Siliziumnitrid gegebenenfalls gleichfalls einsetzbar.In particular, it is also advantageous that the materials are suitable for sintering at high temperatures, wherein, in particular due to the reducing effect, silicon carbide must be emphasized. Alternatively, silicon nitride may optionally be used as well.

Ein Verfahren der eingangs genannten Art zeichnet sich dadurch aus, dass die Schale nach Einbringen des Sinterguts in diese von einem Verschlusselement abgedeckt wird, so dass hierüber oder zumindest über eine Öffnung in dem Verschlusselement oder über eine Öffnung in der Schale Schutzgas ins Innere der Schale, also den ersten Innenraum, eindringt, dass die topfförmige Abdeckung unmittelbar mit ihrem Rand gasdicht auf die Basisplatte abgestützt ist, und dass der von der topfförmigen Abdeckung umgebene zweite Innenraum mit einem ein Anheben der Abdeckung ausschließenden Überdruck mit dem Schutzgas beaufschlagt wird, insbesondere mit einem Überdruck p mit 1 mbar ≤ p ≤ 25 mbar , insbesondere 2 mbar ≤ p ≤10 mbar über Umgebungsdruck.A method of the type mentioned above is characterized in that the shell is covered after introduction of the sintered material in this by a closure element, so that over or at least via an opening in the closure element or via an opening in the shell shielding gas into the interior of the shell, so the first interior, Penetrates that the cup-shaped cover is directly supported gas-tight with its edge on the base plate, and that the surrounded by the cup-shaped cover second interior is acted upon by a lifting of the cover excluding overpressure with the protective gas, in particular with an overpressure p with 1 mbar ≤ p ≤ 25 mbar, in particular 2 mbar ≤ p ≤ 10 mbar above ambient pressure.

Insbesondere ist vorgesehen, dass als Sintergut ein größeres Objekt, insbesondere ein dentales Brückengerüst, insbesondere ein Brückengerüst mit zumindest drei Brückengliedern, vorzugsweise zumindest fünf Brückengliedern, verwendet wird, und dass das Sintergut in einem die Vorrichtung aufnehmenden, also diese umgebenden Sinterraum von Zimmertemperatur TZ auf eine Temperatur T1 mit 800 °C ≤ T1 ≤ 1100 °C mit einer Heizrate R1 mit 5 K/min ≤ R1 ≤ 100 K/min, insbesondere 20 K/min ≤ R1 ≤ 80 K/min, aufgeheizt, nach gegebenenfalls einer Haltezeit t1 bei der Temperatur T1 mit 1 min ≤ t1 ≤ 10 min auf eine Temperatur T2 mit 1200 °C ≤ T2 ≤ 1350 °C mit einer Heizrate R2 mit 5 /min ≤ R2 ≤ 30 K/min aufgeheizt wird, das Sintergut bei der Temperatur T2 für eine Zeit t2 mit 5 min ≤ t2 ≤ 120 min, insbesondere 15 min ≤ t2 ≤ 50 min gehalten wird, wobei gegebenenfalls das Sintergut anschließend, also nach der Haltezeit t2, auf eine Temperatur T3 mit T3 > T2 zum oberflächlichen Schmelzen des Sinterguts erhitzt wird, und sodann von der Temperatur T2 bzw. T3 auf eine Temperatur unterhalb 400 °C mit einer Abkühlrate R3 abgekühlt wird, die vorzugsweise zumindest zu Beginn des Abkühlens 5 K/min ≤ R3 ≤ 100 K/min beträgt. Es erfolgt sodann ein Abkühlen auf Zimmertemperatur Tz.In particular, it is provided that a larger object, in particular a dental bridge framework, in particular a bridge framework with at least three bridge members, preferably at least five bridge members, is used, and that the sintered material in a device receiving, so these surrounding sintering chamber of room temperature T Z to a temperature T 1 at 800 ° C ≤ T 1 ≤ 1100 ° C with a heating rate R 1 with 5 K / min ≤ R 1 ≤ 100 K / min, in particular 20 K / min ≤ R 1 ≤ 80 K / min, heated , after optionally a holding time t 1 at the temperature T 1 with 1 min ≤ t 1 ≤ 10 min to a temperature T 2 at 1200 ° C ≤ T 2 ≤ 1350 ° C with a heating rate R 2 with 5 / min ≤ R 2 ≤ 30 K / min is heated, the sintered material at the temperature T 2 for a time t 2 with 5 min ≤ t 2 ≤ 120 min, in particular 15 min ≤ t2 ≤ 50 min is maintained, where appropriate, the sintered material then, ie after the holding time t 2 , to a temperature T 3 with T 3 > T 2 is heated to superficial melting of the sintered material, and then cooled from the temperature T 2 and T 3 to a temperature below 400 ° C at a cooling rate R 3 , preferably at least at the beginning of the cooling. 5 K / min ≤ R 3 ≤ 100 K / min. It then takes place cooling to room temperature T z .

Die Erfindung sieht auch vor, dass das Sintergut zum Sintern in einem die Vorrichtung umgebenden Sinterraum von Zimmertemperatur auf eine Temperatur T2 wie 1200 °C ≤ T2 ≤ 1350 °C mit einer Heizrate R1 aufgeheizt wird, bei der Temperatur T2 über eine Zeit t2 mit 5 min ≤ t2 ≤ 220 min, insbesondere 15 min ≤ t2 ≤ 60 min gehalten wird, wobei gegebenenfalls das Sintergut anschließend, also nach der Haltezeit, auf eine Temperatur T3 mit T3 > T2 zum oberflächlichen Schmelzen des Sinterguts erhitzt wird, und sodann von der Temperatur T2 bzw. T3 auf eine Temperatur unterhalb 400 °C mit einer Abkühlrate R3 abgekühlt wird, wobei die Abkühlrate R3 vorzugsweise anfänglich 5 K/min ≤ R3 ≤ 100 K/min beträgt.The invention also provides that the sintered material for sintering in a sintering space surrounding the device from room temperature to a temperature T 2 such as 1200 ° C ≤ T 2 ≤ 1350 ° C is heated at a heating rate R 1 , at the temperature T 2 via a Time t 2 with 5 min ≤ t 2 ≤ 220 min, in particular 15 min ≤ t 2 ≤ 60 min is maintained, where appropriate, the sintered material then, ie after the holding time, to a temperature T 3 with T 3 > T 2 for superficial melting is then heated from the temperature T 2 or T 3 to a temperature below 400 ° C at a cooling rate R 3 , wherein the cooling rate R 3 is preferably initially 5 K / min ≤ R 3 ≤ 100 K / min is.

Dabei ist insbesondere vorgesehen, dass die Heizrate R1 auf einen Wert mit 5 K/min ≤ R1 ≤ 100 K/min, insbesondere 20 K/min ≤ R1 ≤ 80 K/min eingestellt wird.It is provided in particular that the heating rate R 1 is set to a value of 5 K / min ≦ R 1 ≦ 100 K / min, in particular 20 K / min ≦ R 1 ≦ 80 K / min.

Das Aufheizen auf eine Temperatur T1 und das gegebenenfalls erfolgende Halten bei der Temperatur T1, um sodann auf eine Temperatur T2 weiter aufgeheizt zu werden, wird für größere Objekte wie Brückengerüste bevorzugt durchgeführt.The heating to a temperature T 1 and the optionally held at the temperature T 1 , and then further heated to a temperature T 2 , is preferably carried out for larger objects such as bridge frameworks.

Das zunächst erfolgende Aufheizen auf die Temperatur T1 und sodann auf die Temperatur T2 mit einer gegebenenfalls abweichenden Aufheizrate kann dahingehend geändert werden, dass unmittelbar ein Aufheizen auf die Temperatur T2 erfolgt, sofern es sich bei dem Sintergut um kleinere Objekte, wie ein Gerüst für einen Zahn, handelt.The initial heating to the temperature T 1 and then to the temperature T 2 with a possibly different heating rate can be changed to the effect that directly to a temperature T 2 takes place, if it is the sintered to smaller objects, such as a scaffold for a tooth, act.

Das kurzzeitige Aufschmelzen der Oberfläche, das unabhängig von der Größe des Objekts durchgeführt werden kann, stellt dabei einen eigenerfinderischen Vorschlag dar, der auch dann zur Anwendung gelangen kann, wenn zum Sintern eine Vorrichtung benutzt wird, die von der erfindungsgemäßen Lehre abweicht.The brief melting of the surface, which can be carried out regardless of the size of the object, thereby represents a self-inventive suggestion, which can also be used when a device is used for sintering, which differs from the teaching of the invention.

Zusätzlich kann vorgesehen sein, dass nach dem Abkühlen des Sinterguts auf die Temperatur T1 die Basisplatte mit der Schale, deren Verschlusselement und der Abdeckung aus dem Sinterraum zumindest bereichsweise, vorzugsweise vollständig entfernt wird. Der Sinterraum kann Innenraum eines Sinterofens sein, der als dritter Innenraum zu bezeichnen ist.In addition, it can be provided that, after cooling of the sintered material to the temperature T 1, the base plate with the shell, its closure element and the cover from the sintering space at least partially, preferably completely removed. The sintering space may be the interior of a sintering furnace, which may be referred to as a third interior space.

Unabhängig von den zuvor angegebenen Temperaturen und Heizraten ist als eigenerfinderisches Merkmal noch hervorzuheben, dass die Möglichkeit besteht, nach dem Dichtsintern ein zusätzliches Aufheizen durchzuführen, auf Grund dessen das Sintergut oberflächlich schmilzt, um gewünschte Oberflächeneigenschaften zu erzielen.Regardless of the above-mentioned temperatures and heating rates, it should be emphasized as an inventive feature that it is possible to carry out additional heating after dense sintering, as a result of which the sintered material melts superficially in order to achieve desired surface properties.

Die kurzzeitig hohen Temperaturen im Inneren der Schale führen zu einem oberflächlichen Schmelzen, so dass bei Gerüsten die Oberfläche annähernd wie bereits zahntechnisch poliert erscheint.The short-term high temperatures inside the shell lead to a superficial melting, so that in the case of scaffolds the surface almost appears to be already polished by dental technology.

Insbesondere ist vorgesehen, dass die Schutzgaseinlass- und/oder -auslassöffnung mit einer Zu- bzw. Ableitung verbunden ist, die aus Aluminiumoxid besteht. Dabei kann die Leitung mit einem Hochtemperaturklebstoff, insbesondere auf Aluminiumoxidbasis, mit der Basisplatte verbunden werden.In particular, it is provided that the Schutzgaseinlass- and / or -auslassöffnung is connected to an inlet and outlet, which consists of aluminum oxide. In this case, the line can be connected to the base plate with a high-temperature adhesive, in particular based on alumina.

Bei der Wahl von SiC als Material für die Basisplatte, die Abdeckung, die Schale und deren Verschlusselement nutzt man die gute Wärmeleitfähigkeit und nahezu vollständige Dichtheit des Materials aus. Infolgedessen werden Temperaturunterschiede innerhalb der Bauteile minimiert. Thermische Spannungen werden dadurch reduziert. Infolgedessen sind schnelle Temperaturwechsel auch bei großen Bauteilen von z. B. Durchmesser von 100 mm möglich. Ferner zeigt SiC einen Reduziereffekt und ist in der Lage, Restsauerstoff in der Atmosphäre mit dem enthaltenen Kohlenstoff zu Kohlenmonoxid umzuwandeln. Dieser Effekt geht nicht verloren. Gleichzeitig ist keine messbare Abnahme der Wandstärken der Materialien feststellbar.When choosing SiC as the material for the base plate, the cover, the shell and its closure element, one makes use of the good thermal conductivity and almost complete tightness of the material. As a result, temperature differences within the components are minimized. Thermal stresses are thereby reduced. As a result, rapid temperature changes even with large components of z. B. diameter of 100 mm possible. Further, SiC exhibits a reducing effect and is capable of converting residual oxygen in the atmosphere with the contained carbon to carbon monoxide. This effect is not lost. At the same time, no measurable decrease in the wall thicknesses of the materials can be detected.

Die Lagerung des Sinterguts in einer nicht dicht verschlossenen Sinterschale verbessert das Sinterergebnis. Grund für die Verbesserung kann die Schaffung eines in Bezug auf Sauerstoff mit reduzierenden Wänden versehenen Innenraums sein. Es erfolgt eine Abschwächung der Störung durch Sauerstoff. Entsprechende Störungen können das Sintergut nicht mehr direkt erreichen. Es steigt die Wahrscheinlichkeit, dass die Störungen ausgewaschen und somit gemildert werden.The storage of the sintered material in a not sealed sealed sintering bowl improves the sintering result. The reason for the improvement may be the creation of an interior provided with reducing-wall oxygen. There is a weakening of the disturbance by oxygen. Corresponding disturbances can no longer reach the sintered material directly. It increases the probability that the disturbances are washed out and thus mitigated.

Das kontrollierte Zuführen und Abführen von Inertgas stellt sicher, dass der Innendruck in der Abdeckung nicht derart ansteigen kann, dass diese angehoben wird. Auf diese Weise gelingt ein Sauerstoffausschluss. Anstelle von einer oder mehrerer Schutzgasableitungsöffnungen in der Basisplatte kann auch in der Abdeckung z. B. zumindest eine durch Laser ausgebildete Öffnung vorhanden sein, um kontrolliert Inertgas auslassen zu können.The controlled supply and removal of inert gas ensures that the internal pressure in the cover can not rise so that it is raised. In this way, an oxygen exclusion succeeds. Instead of one or more protective gas discharge openings in the base plate can also in the cover z. B. at least one opening formed by laser be present in order to be able to omit controlled inert gas.

Abweichend von üblichen Techniken werden keine Hohlkugeln zum Lagern des Sinterguts in der Schale eingesetzt. Hohlkugeln können Sauerstoff speichern und vergiften somit bei hohen Temperaturen die Atmosphäre in unmittelbarer Nähe des Sinterguts. Erfindungsgemäß werden dichte Kugeln eingesetzt, die Sauerstoff nicht speichern können. Dabei zeigt sich Zirkoniumoxid als Material für die Kugeln überraschenderweise als geeignet, obwohl dieses anfänglich in sauerstoffarmer Atmosphäre zur Sauerstoffabgabe neigt. Nach erfolgter Sauerstoffabgabe, die z. B. durch einen Temperaturzyklus erzielt wird, zeigen entsprechende Vollkugeln aus Zirkoniumoxid reduzierende Wirkung für Sauerstoff.Unlike conventional techniques, no hollow balls are used for storing the sintered material in the shell. Hollow balls can store oxygen and thus poison the atmosphere in the immediate vicinity of the sintered material at high temperatures. According to the invention, dense spheres are used which can not store oxygen. In this case, zirconium oxide is surprisingly suitable as the material for the spheres, although this initially tends to give off oxygen in an oxygen-poor atmosphere. After the oxygen release, the z. B. achieved by a temperature cycle, corresponding solid spheres of zirconia show reducing effect for oxygen.

Um die Abdeckung und die Schale ordnungsgemäß auf der Basisplatte zu positionieren, sieht der Stand der Technik üblicherweise Stufen vor. Hiervon löst sich die Erfindung und setzt eine ebene Platte ein, die auf einfache Weise im Bereich der Kontaktflächen mit der Abdeckung poliert werden kann, damit in einem Umfang eine Abdichtung erfolgt, dass ein Eindringen von Sauerstoff dem Grunde nach nicht oder nicht wesentlich möglich ist. Da keine Stufen vorhanden sind, ergeben sich auch keine Dickenunterschiede in der Basisplatte, so dass infolgedessen thermische Spannungen reduziert werden.To properly position the cover and tray on the base plate, the prior art usually provides for steps. From this, the invention dissolves and uses a flat plate which can be easily polished in the area of the contact surfaces with the cover so that a seal is made to an extent that the penetration of oxygen is basically not or not substantially possible. Since there are no steps, there are no differences in thickness in the base plate, as a result, thermal stresses are reduced.

Weitere Einzelheiten, Vorteile und Merkmale der Erfindung ergeben sich nicht nur aus den Ansprüchen, den diesen zu entnehmenden Merkmalen - für sich und/oder in Kombination -, sondern auch aus der nachfolgenden Beschreibung von den Zeichnungen zu entnehmenden bevorzugten Ausführungsbeispielen.For more details, advantages and features of the invention will become apparent not only from the claims, the features to be taken these features - alone and / or in combination - but also from the following description of the drawings to be taken preferred embodiments.

Es zeigen:

Fig. 1
eine erste Ausführungsform einer Vorrichtung zum Sintern von Sintergut,
Fig. 2
eine zweite Ausführungsform einer entsprechenden Vorrichtung und
Fig. 3
ein Zeittemperaturdiagramm.
Show it:
Fig. 1
a first embodiment of a device for sintering of sintered material,
Fig. 2
a second embodiment of a corresponding device and
Fig. 3
a time temperature diagram.

In den Fig. 1 und 2, in denen grundsätzlich für gleiche Elemente gleiche Bezugszeichen verwendet werden, ist jeweils rein prinzipiell eine Ausführungsform einer Vorrichtung 10, 100 dargestellt, mit der metallisches Sintergut, insbesondere Zahngerüste gesintert werden. Wie sich aus der Fig. 1 prinzipiell ergibt, befindet sich die Vorrichtung 10 - entsprechend die Vorrichtung 100 - in einem Innen- oder Sinterraum 12 eines Sinterofens, von dem Abschnitte von Wandungen 15, 17 prinzipiell dargestellt sind. In dem Sinterraum 12, der auch als dritter Innenraum bezeichnet wird, werden die erforderlichen Temperaturen eingestellt, um in der Vorrichtung 10, 100 vorhandenes Sintergut im erforderlichen Umfang zu sintern.In the Fig. 1 and 2 , in which the same reference numerals are used in principle for the same elements, an embodiment of a device 10, 100 is shown purely in principle, are sintered with the metallic sintered material, in particular toothed scaffolds. As is clear from the Fig. 1 In principle, the device 10 is - corresponding to the device 100 - in an inner or sintered space 12 of a sintering furnace, of which sections of walls 15, 17 are shown in principle. In the sintering space 12, which is also referred to as the third interior, the required temperatures are set to sinter in the apparatus 10, 100 existing sintered material to the extent required.

Die Vorrichtung 10 besteht aus einer Basisplatte 14, einer als Glocke zu bezeichnenden topf- oder haubenförmigen Abdeckung 16, einer im Schnitt U-förmigen Schale 18 sowie einem als Verschlusselement bezeichneten Deckel 20, mittels dessen die Schale 18 grundsätzlich nicht völlig dicht verschlossen wird.The device 10 consists of a base plate 14, a bell to be designated cup or dome-shaped cover 16, a sectionally U-shaped shell 18 and a lid 20 designated as a closure element, by means of which the shell 18 is not completely sealed in principle.

Des Weiteren ist die Schale 18 über ein Ringelement 22 auf der Basisplatte 14 abgestützt. Das Ringelement 22 weist Aussparungen 24, 26, 28 auf, damit eine Verbindung zwischen dem von der Glocke 16 umgebenen Innenraum 30 - als zweiter Innenraum bezeichnet - und dem von dem Ringelement 22 umgebenen Raum 32 besteht. In dem von der Schale 18 umgebenen und von dem Deckel 20 abgeschlossenen Innenraum 34, der als erster Innenraum bezeichnet wird, wird das in Fig. 1 nicht dargestellte Sintergut angeordnet.Furthermore, the shell 18 is supported on the base plate 14 via a ring element 22. The ring element 22 has recesses 24, 26, 28, so that a connection between the space surrounded by the bell 16 interior 30 - referred to as the second interior - and the area surrounded by the ring member 22 space 32 consists. In the surrounded by the shell 18 and closed by the lid 20 interior 34, which is referred to as the first interior, the in Fig. 1 arranged sintered material, not shown.

Entsprechend der erfindungsgemäßen Lehre sind die Basisplatte 14, die Glocke 16, die Schale 18, der Deckel 20 sowie das Ringelement 22 bevorzugterweise aus SiC hergestellt, gleichwenn als alternative Materialien auch SiN in Frage kommen kann.According to the teaching of the invention, the base plate 14, the bell 16, the shell 18, the cover 20 and the ring member 22 are preferably made of SiC, same as SiN may come as alternative materials.

Die Basisplatte 14 und der umlaufende Rand 36 der Glocke 16 sind in einem Umfang plan geschliffen, dass ein formschlüssiges Aufstehen der Glocke 16 auf der Basisplatte 14 sichergestellt ist. Hierdurch wird dem Grunde nach ein Eindringen von Sauerstoff verhindert.The base plate 14 and the peripheral edge 36 of the bell 16 are ground flat in a circumference that a positive standing up of the bell 16 is secured to the base plate 14. As a result, an intrusion of oxygen is basically prevented.

Erfindungsgemäß sollte der Deckel 20 den (ersten) Innenraum 34 der Schale 18 nicht vollständig abdichten, so dass strömungstechnisch eine Verbindung zwischen dem (zweiten) Innenraum 30, der sich zwischen der Schale 18 und der Glocke 16 erstreckt, mit dem von der Schale 18 umgebenden ersten Innenraum 34 besteht. Liegt der Deckel 20 abdichtend auf der Schale 18, so weist der Deckel 20 zumindest eine Durchbrechung auf, damit ein Durchspülen des Innenraums 34 der Schale 18 erfolgen kann. Äquivalent wäre eine Durchbrechung in der Schale 18.According to the invention, the cover 20 should not completely seal off the (first) inner space 34 of the shell 18, so that fluidically a connection between the (second) inner space 30, which extends between the shell 18 and the bell 16, with that of the shell 18 surrounding first interior 34 consists. If the cover 20 sealingly rests on the shell 18, then the cover 20 has at least one opening, so that a flushing of the interior 34 of the shell 18 can take place. Equivalent would be an opening in the shell 18th

Um Oxidation und Verfärbungen zu vermeiden, wird dem zweiten Innenraum 30 über eine im Ausführungsbeispiel in der Basisplatte 14 vorhandene Öffnung 38 ein Schutzgas wie z.B. Argon oder Stickstoff zugeführt. Dieses Schutzgas gelangt in den von der Schale 18 umgebenen ersten Innenraum 34, da erwähntermaßen der Deckel 20 die Schale 18 nicht abdichtet. Alternativ oder ergänzend gelangt das Schutzgas über die zumindest eine Durchbrechung in dem Deckel 20 und/oder in der Wandung der Schale 18.In order to avoid oxidation and discoloration, the second internal space 30 is provided with an inert gas, such as an opening 38, provided in the base plate 14 in the exemplary embodiment. Supplied with argon or nitrogen. This protective gas enters the first inner space 34 surrounded by the shell 18, since, as mentioned, the cover 20 does not seal the shell 18. Alternatively or additionally, the protective gas passes through the at least one opening in the cover 20 and / or in the wall of the shell 18th

Das dem zweiten Innenraum 30 zugeführte Gas strömt sodann über eine vorzugsweise gleichfalls in der Basisplatte 14 vorhandene Öffnung aus. Es besteht jedoch auch die Möglichkeit, in der Umfangswandung der Glocke 16 z.B. mittels Laser zumindest eine Öffnung zu bilden, über die Gas ausströmt. Dabei wird das ausströmende Gas vorzugsweise derart in den Sinterraum 12 - also den dritten Innenraum - geleitet, dass die Glocke 16 zumindest im Bereich deren umlaufenden Randes 30 mit Schutzgas umspült wird.The gas supplied to the second internal space 30 then flows out via an opening which is likewise preferably present in the base plate 14. However, it is also possible to fit in the circumferential wall of the bell 16, e.g. to form by laser at least one opening through which gas flows. In this case, the outflowing gas is preferably directed into the sintering space 12 - that is, the third interior space - in such a way that the bell 16 is surrounded with inert gas at least in the region of its peripheral edge 30.

Dadurch, dass der Deckel 20 nicht abdichtend auf der Schale 18 aufliegt, kann Schutzgas in den von der Schale 18 umgebenen ersten Innenraum 34 strömen, in dem sich das Sintergut befindet. Gleichzeitig wird jedoch ein Eindringen von Sauerstoff (Störungen) reduziert. Entsprechendes gilt in Bezug auf die zumindest eine Durchbrechung.Due to the fact that the cover 20 does not rest in a sealing manner on the shell 18, protective gas can flow into the first interior space 34 surrounded by the shell 18, in which the sintered material is located. At the same time, however, the penetration of oxygen (disturbances) is reduced. The same applies with regard to the at least one opening.

Der (zweite) Innenraum 30 sollte gegenüber der Umgebung einen erhöhten Druck aufweisen, wobei ein Überdruck zwischen 1 mbar und 25 mbar, insbesondere zwischen 2 mbar und 10 mbar zu bevorzugen ist.The (second) inner space 30 should have an increased pressure relative to the environment, with an overpressure between 1 mbar and 25 mbar, in particular between 2 mbar and 10 mbar, being preferred.

Das Ausführungsbeispiel der Fig. 2 unterscheidet sich von dem der Fig. 1 dahingehend, dass die Schale 18 nicht auf einem Ring 22, sondern über von der Bodenwandung 40 der Schale 18 abragende Vorsprünge 42, 44 abgestützt ist. Dabei sind insbesondere drei Vorsprünge vorgesehen, die gleichmäßig verteilt auf einem Kreis angeordnet sind. Ansonsten entspricht die Ausführungsform der der Fig. 1, so dass auf die diesbezüglichen Erläuterungen verwiesen wird.The embodiment of Fig. 2 is different from that of Fig. 1 to the effect that the shell 18 is not supported on a ring 22, but on protrusions 42, 44 protruding from the bottom wall 40 of the shell 18. In this case, in particular, three projections are provided, which are arranged distributed uniformly on a circle. Otherwise, the embodiment corresponds to the Fig. 1 , so that reference is made to the relevant explanations.

Durch die Abstützung der Schale 18 auf dem Ring 22 oder über die Vorsprünge 42, 44 ergibt sich der Vorteil, dass die Basisplatte 14 eine gleichbleibende Dicke aufweist, so dass Dickenunterschiede vermieden und infolgedessen interne Spannungen reduziert werden.By supporting the shell 18 on the ring 22 or over the projections 42, 44 there is the advantage that the base plate 14 has a constant thickness, so that differences in thickness avoided and as a result internal stresses are reduced.

Damit beim Sintern das in dem ersten Innenraum 34 vorhandene Sintergut 46 die Innenflächen der Schale 18 nicht berührt, ist auf der Innenseite 48 der Bodenwandung 40, also der Bodenfläche ein kugeliges Schüttgut 50 eingebracht, das aus Vollkugeln, also nicht aus Hohlkugeln, besteht. Als Materialien kommen bevorzugterweise Aluminiumoxid oder Zirkoniumoxid in Frage. Die Vollkugeln haben den Vorteil, dass Sauerstoff nicht gespeichert werden kann. Dies gilt auch für Zirkoniumoxidkugeln, die zwar in sauerstoffarmer Atmosphäre anfangs zu Sauerstoffabgabe neigen. Nach erfolgter Sauerstoffabgabe zeigen diese jedoch reduzierende Wirkung.So that during sintering, the sintered material 46 present in the first inner space 34 does not touch the inner surfaces of the shell 18, a spherical bulk material 50 is introduced on the inner side 48 of the bottom wall 40, ie the bottom surface, which consists of solid spheres, ie not of hollow spheres. As materials are preferably alumina or zirconia in question. The solid balls have the advantage that oxygen can not be stored. This also applies to zirconium oxide spheres, which initially tend to release oxygen in an oxygen-poor atmosphere. After the release of oxygen, however, these show a reducing effect.

Als bevorzugte Abmessungen der insbesondere aus Siliziumcarbid bestehenden Bauelemente sind anzugeben: Basisplatte 14: Durchmesser 90 mm bis 110 mm, Dicke 2 bis 4 mm; Glocke 16: Außendurchmesser 95 mm bis 105 mm, Wandstärke 3 mm bis 5 mm, Höhe 50 mm bis 55 mm; Ringelement 22: 4 mm bis 8 mm, Außendurchmesser 60 mm bis 70 mm, Wandstärke 3 mm bis 5 mm; Sinterschale 18: Höhe 30 mm bis 35 mm, Außendurchmesser 80 mm bis 90 mm, Wandstärke 3 mm bis 5 mm; Deckel 20: gleich Außendurchmesser Schale 18, Dicke im Randbereich 2 mm bis 5 mm, Dicke Mittenbereich 4 mm bis 8 mm. As preferred dimensions of the components consisting in particular of silicon carbide are to indicate: Base plate 14: Diameter 90 mm to 110 mm, thickness 2 to 4 mm; Bell 16: Outer diameter 95 mm to 105 mm, wall thickness 3 mm to 5 mm, height 50 mm to 55 mm; Ring element 22: 4 mm to 8 mm, outer diameter 60 mm to 70 mm, wall thickness 3 mm to 5 mm; Sinter tray 18: Height 30 mm to 35 mm, outside diameter 80 mm to 90 mm, wall thickness 3 mm to 5 mm; Cover 20: equal outer diameter shell 18, thickness in the edge region 2 mm to 5 mm, thickness center region 4 mm to 8 mm.

Wie sich aus der zeichnerischen Darstellung ergibt, kann der Abstand zwischen Außenfläche der Schale 18 und Innenfläche der Glocke 16 relativ klein gewählt werden. Dies hat den Vorteil, dass hierdurch ein Eindringen von Sauerstoff in den (ersten) Innenraum 34 der Schale 18 zusätzlich behindert wird, insbesondere dann, wenn sich die Schutzgasauslassöffnung im Randbereich der Glocke 16 befindet und diese durchsetzt.As can be seen from the graphic representation, the distance between the outer surface of the shell 18 and the inner surface of the bell 16 can be chosen to be relatively small. This has the advantage that in this way the penetration of oxygen into the (first) interior 34 of the shell 18 is additionally hindered, in particular when the protective gas outlet opening is located in the edge region of the bell 16 and passes through it.

Der Fig. 3 ist eine Heiz- und Kühlkurve zu entnehmen, um das Sintergut 46 zu sintern. Die Kurve gemäß Fig. 3 gilt für ein größeres Objekt, das zu sintern ist. Als Beispiel ist ein zahntechnisches Brückengerüst mit 4 Gliedern zu nennen.Of the Fig. 3 is to take a heating and cooling curve to sinter the sintered 46. The curve according to Fig. 3 applies to a larger object that is to be sintered. An example is a dental bridge framework with 4 members.

Rein prinzipiell ergibt sich, dass der Sinterofen und damit der Sinterraum 12 infolgedessen auch das Sintergut 46 zunächst von Zimmertemperatur TZ auf eine Temperatur T1 aufgeheizt wird, wobei T1 zwischen 800 °C und 1100 °C bei Kobalt-Chrom-Legierungen als Material für das Sintergut 46 liegt. Die Aufheizrate sollte bevorzugterweise zwischen 20 K/min und 80 K/min liegen. Auf der Temperatur T1 wird das Sintergut 46 über eine Zeit t1 zwischen 1 min und 10 min gehalten. Sodann erfolgt eine Aufheizung von der Temperatur T1 auf eine Temperatur T2 zwischen 1200 °C und 1350 °C mit einer Aufheizrate zwischen 5 K/min und 30 K/min. Bei der Temperatur T2 wird das Sintergut 46 über eine Zeit t2 zwischen 5 und 120 min gehalten und sodann auf eine Temperatur unterhalb von 400 °C abgekühlt, wobei zumindest eine Abkühlrate zwischen 5 K/min und 100 K/min zu wählen ist.In principle, it follows that the sintering furnace and thus the sintering chamber 12 as a result, the sintered 46 is first heated from room temperature T Z to a temperature T 1 , wherein T 1 between 800 ° C and 1100 ° C for cobalt-chromium alloys as material for the sintered 46 lies. The heating rate should preferably be between 20 K / min and 80 K / min. At the temperature T 1 , the sintered material 46 is held for a time t 1 between 1 min and 10 min. Then there is a heating from the temperature T 1 to a temperature T 2 between 1200 ° C and 1350 ° C with a heating rate between 5 K / min and 30 K / min. At the temperature T 2 , the sintered material 46 is kept for a time t 2 between 5 and 120 minutes and then cooled to a temperature below 400 ° C, wherein at least a cooling rate between 5 K / min and 100 K / min is to be selected.

Sodann erfolgt eine Abkühlung auf Zimmertemperatur, wobei bevorzugterweise die Vorrichtung 10, 100 aus dem Sinterraum 12 entfernt wird. Hierzu kann die Vorrichtung 10, 100 abgesenkt werden, wie durch den Doppelpfeil 52 symbolisiert wird. Gegebenenfalls kann das Sintergut nach dem Abkühlen auf die Temperatur T1 über eine Zeit zwischen 1 min und 10 min bei der Temperatur T1 gehalten werden. Sodann erfolgt ein Abkühlen auf Zimmertemperatur TZ.Then it is cooled to room temperature, wherein preferably the device 10, 100 is removed from the sintering space 12. For this purpose, the device 10, 100 can be lowered, as symbolized by the double arrow 52. Optionally, the sintered body can be produced by cooling to the temperature T 1 for a time between 1 min and 10 min at the temperature T 1 is kept. Then it is cooled to room temperature T Z.

Wie sich aus der Prinzipdarstellung der Fig. 3 ergibt, kann das Sintergut nach Erreichen der Sintertemperatur T2 kurzfristig auf eine höhere Temperatur T3 (gestrichelter Bereich) erhitzt werden, um ein oberflächliches Schmelzen zu erreichen. Das kurzzeitige gezielte Anschmelzen kann während der Haltezeit t2, vorzugsweise nach der Haltezeit t2 durchgeführt werden. Letzteres ergibt sich aus der Fig. 3.As can be seen from the schematic diagram of the Fig. 3 results in the sintered material after reaching the sintering temperature T 2 short-term to a higher temperature T 3 (dashed area) are heated to achieve a superficial melting. The brief targeted melting can be carried out during the holding time t 2 , preferably after the holding time t 2 . The latter results from the Fig. 3 ,

Das Aufheizen auf die Temperatur T1, Halten bei dieser Temperatur und sodann das weitere Aufheizen auf die Temperatur T2 mit gegebenenfalls voneinander abweichenden Aufheizraten beim Sintern kleiner Objekte, wie ein Gerüst für einen Zahn, ist nicht erforderlich. Vielmehr kann ein unmittelbares Aufheizen von der Zimmertemperatur auf die Temperatur T2 erfolgen. Unabhängig hiervon besteht gleichfalls die Möglichkeit, nach dem Halten auf der Temperatur T2 eine kurzfristige Temperaturerhöhung auf eine Temperatur T3 durchzuführen, um ein oberflächliches Aufschmelzen des Sintergutes zu erreichen.The heating to the temperature T 1 , holding at this temperature and then the further heating to the temperature T 2 with possibly different heating rates when sintering small objects, such as a framework for a tooth, is not required. Rather, a direct heating from the room temperature to the temperature T 2 take place. Irrespective of this, it is likewise possible to carry out a short-term temperature increase to a temperature T 3 after holding at the temperature T 2 in order to achieve superficial melting of the sintered material.

Claims (15)

  1. A device (10,100) for sintering sinter products, comprising
    - a tray (18), which accommodates the sinter products, is arranged on a base plate (14), with an interior chamber (34) accommodating the sinter products as the first interior chamber,
    - a pot-shaped cover (16), which encompasses the tray and possesses a rim (36) that is sealed with respect to the base plate,
    - with openings (38) for protective-gas supply and protective-gas discharge lines connected to the interior chamber (30) encompassed by the pot-shaped cover as the second interior chamber, as well as
    - the sintering chamber (12) surrounding the pot-shaped cover with base plate as the third internal chamber,
    characterized in that
    the pot-shaped cover (16) directly rests on the base plate (14) by way of its rim (36), that the tray (18) is covered by a capping element (20), and that the first interior space (34) is connected to the second interior chamber in a gas-flow-allowing manner when the tray is covered by the capping element.
  2. The device according to claim 1,
    characterized in that
    the sinter product (46) is a sinter product out of the group made up of material susceptible to oxidation, metallic sinter product, dental framework.
  3. The device according to at least claim 1,
    characterized in that
    the cover (16) directly rests in a form-fitting manner on the base plate (14).
  4. The device according to at least one of the preceding claims,
    characterized in that
    the tray (18) is supported on a ring (22), which possesses openings (24, 26, 28) and in turn is arranged on the base plate (14), whereby especially through the base plate (14.) inside of the ring passes the protective gas supply opening (38) and possibly the protective gas discharge opening.
  5. The device according to at least one of the preceding claims,
    characterized in that
    projections (42, 44) originate from the tray (18) or its bottom wall (40), preferably three projections arranged equidistant on a circle, via which the tray is supported on the base plate (14).
  6. The device according to at least one of the preceding claims,
    characterized in that
    in the tray (18) the sinter product (46) is arranged on bulk material (50) in form of solid balls of ceramics, in particular of zirconia or Al2O3.
  7. The device according to at least one of the preceding claims,
    characterized in that
    the base plate (14), the tray (18), the capping element (20), and the pot-shaped cover (16) consist of a material out of the group that is made up of SiC, SiN.
  8. A method for sintering sinter products (46), utilizing a device (10,100) that comprises a tray (18), which is arranged on a base plate (14) and possesses an interior chamber (34) as the first interior chamber, into which the sinter product is introduced, a pot-shaped cover (16) surrounding the tray with a rim (36) that is sealed with respect to the base plate, as well as protective-gas supply and discharge openings connected to the interior chamber (30) surrounded by the cover as the second interior chamber, whereby protective gas flows through the second interior chamber that is surrounded by the pot-shaped cover,
    characterized in that
    the tray (18), after the sinter product (46) has been placed into it, is covered by a capping element (20), via which, or via at least one opening in the capping element, or via at least one opening in the tray, protective gas enters the interior chamber (34) of the tray, that the pot-shaped cover (16) directly rests on the baseplate (14) by way of its rim, and that the second interior chamber (10) surrounded by the pot-shaped cover is charged with protective gas to an excess that rules out a lifting of the cover.
  9. The method according to claim 8,
    characterized in that
    a pressure burden p with 1 mbar ≤ p ≤ 25 mbar is admitted to the second interior chamber (30).
  10. The method according to claim 8 or 9,
    characterized in that
    as sinter product (46) one uses a sinter product selected from the group made up of material susceptible to oxidation, metallic sinter product, especially as sinter product one uses a product that consists of a cobalt chromium alloy, preferably a CoCrMo alloy.
  11. The method according to at least claim 8,
    characterized in that
    as sinter product one uses a larger object, in particular a dental bridge framework, in particular a bridge framework with at least three bridge elements, in particular five bridge elements, and that the sinter products are heated in a sintering chamber surrounding the device from room temperature to a temperature T1 with 800 °C ≤ T1 ≤ 1100 °C at a heating rate R1 with 5 K/min ≤ R1 ≤ 100 K/min, in particular 20 K/min ≤ R1 ≤ 80 K/min, after a possible holding time t1 at the temperature T1 with 1 min ≤ t1 ≤ 10 min is heated to a temperature T2 with 1200 °C ≤ T2 ≤ 1350 °C at a heating rate R2 with 5 /min ≤ R2 ≤ 30 K/min, the sinter product is held at the temperature T2 for a time period T2 with 5 min ≤ t2 ≤ 120 min, in particular 15 min ≤ t2 ≤ 50 min, whereby possibly the product to be sintered subsequently is heated to a temperature T3 with T3 > T2 to melt the surface of the product to be sintered, and subsequently is cooled from the temperature T2 or T3 to a temperature below 400 °C with a cooling rate R3, which preferably at least at the beginning of the cool-down amounts to 5 K/min ≤ R3 ≤ 100 K/min.
  12. The method according to at least claim 11,
    characterized in that
    the sinter product during sintering in a sintering chamber surrounding the device is heated from room temperature to a temperature T2 with 1200 °C ≤ T2 ≤ 1350 °C at a heating rate R2, is held at the temperature T2 for a time period t2 with 5 min ≤ t2 ≤ 220 min, in particular 15 min ≤ t2 ≤ 60 min, whereby the sinter product subsequently possibly is heated to a temperature T3 with T3 > T2 to melt the surface of the sinter product, and subsequently is cooled from the temperature T2 or T3 to a temperature below 400 °C at a cooling rate R3, whereby the cooling rate R3 preferably initially has 5 K/min ≤ R3 ≤ 100 K/min.
  13. The method according to claim 12,
    characterized in that
    the heating rate R2 is set to a value with 5 K/min ≤ R2 ≤ 100 K/min, in particular 20 K/min ≤ R2 ≤ 80 K/min.
  14. The method according to at least claim 8,
    characterized in that
    for cooling to room temperature T2 or during the cooling the sinter products, the base plate with the tray, the latter's capping element, and the cover are removed from the sintering chamber at least in parts, preferably entirely.
  15. The method according to claim 9,
    characterized in that
    the second interior chamber (30) surrounded by the cover (10) is charged with a pressure p with 2 mbar ≤ p ≤ 10 mbar, relative to the ambient pressure.
EP12194369.0A 2011-12-09 2012-11-27 Apparatus and method for sintering sinter material Active EP2602036B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE102011056211A DE102011056211B3 (en) 2011-12-09 2011-12-09 Method and apparatus for sintering sintered material

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EP2602036A1 EP2602036A1 (en) 2013-06-12
EP2602036B1 true EP2602036B1 (en) 2018-01-10

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EP (1) EP2602036B1 (en)
JP (1) JP2013122090A (en)
CN (1) CN103162537B (en)
AU (1) AU2012254860B2 (en)
BR (1) BR102012031307A2 (en)
CA (1) CA2796762A1 (en)
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CN103162537A (en) 2013-06-19
AU2012254860A1 (en) 2013-06-27
RU2608863C2 (en) 2017-01-25
DE102011056211B3 (en) 2013-02-07
JP2013122090A (en) 2013-06-20
EP2602036A1 (en) 2013-06-12
US9321104B2 (en) 2016-04-26
CN103162537B (en) 2016-09-07
BR102012031307A2 (en) 2015-01-13
US20130149186A1 (en) 2013-06-13
AU2012254860B2 (en) 2015-03-26
RU2012153051A (en) 2014-06-20
CA2796762A1 (en) 2013-06-09

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